Method and system for providing torque to clutch in hybrid vehicle

ABSTRACT

A method includes estimating a first pressure at a first location of a clutch based on a flow rate of a fluid in the clutch, computing a first torque lead value based on the first pressure, computing a second torque lead value based on a second pressure, computing a third torque lead value by combining the first torque lead value and the second torque lead value, and applying torque from a motor of the vehicle based on the third torque lead value.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/330,315, filed May 25, 2021 and titled “METHOD AND SYSTEM FORPROVIDING TORQUE TO CLUTCH IN HYBRID VEHICLE”, the contents of which areincorporated herein by reference in its entirety.

FIELD

The present application is related to hybrid vehicles. The presentapplication is related more particularly to managing transitions betweenelectric and combustion driving modes.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Hybrid vehicles include an electric motor and a combustion engine. Thehybrid vehicles can be operated in various modes including being poweredby the electric motor only, being powered by the combustion engine only,or being powered by both the electric motor and the combustion engine.Smooth transitions between the various modes can be difficult to manage.If the transition is not smooth, then the vehicle may experience suddenunwanted acceleration or deceleration.

SUMMARY

This section provides a general summary of the disclosure and is not acomprehensive disclosure of its full scope or all of its features.

In one form, the present disclosure provides a method includingestimating a first pressure at a first location of a clutch based on aflow rate of a fluid in the clutch, computing a first torque lead valuebased on the first pressure, computing a second torque lead value basedon a second pressure, computing a third torque lead value by combiningthe first torque lead value and the second torque lead value, andapplying torque from a motor of the vehicle based on the third torquelead value.

In variations of the method of the above paragraph, which can beimplemented individually or in any combination: the method furtherincludes computing the third torque lead value with a powertrain controlmodule coupled to the clutch and a combustion engine; the method furtherincludes providing the third torque lead value from the powertraincontrol module to a hybrid powertrain control module of the vehicle; themethod further includes controlling with the hybrid powertrain controlmodule, the motor to provide the torque to the clutch based on the thirdtorque lead value; the method further includes driving an axle of thevehicle with the motor prior to computing the third torque lead value,and enabling a combustion engine of the vehicle to drive the axle bycoupling the combustion engine with a drivetrain of the vehicle with theclutch, the third torque lead value compensates for the clutch couplingthe combustion engine to the drivetrain; the method further includesdriving an axle with both a combustion engine and the motor afterenabling the combustion engine to drive the axle; the method furtherincludes generating the first and second torque lead values based, inpart, on a time delay value corresponding to a delay in providing torquefrom the motor; the method further includes generating the first andsecond torque lead values based, in part, on the time delay value and aselected lead time value less than the time delay value; the methodfurther includes generating the first torque lead value by generating afirst pressure lead value based on a piston pressure and a selected leadtime, and applying a transfer function to the first pressure lead value,and generating the second torque lead value by generating a secondpressure lead value based on a pressure at a valve and the selected leadtime, and applying a transfer function to the second pressure leadvalue; the flow rate of the fluid in the clutch of the vehicle isestimated by sensing a pressure of the fluid in a fluid line of theclutch; the second pressure is estimated at a second location of theclutch, the second location being different than the first location; thefirst location is at a piston of the clutch and the second location isat a valve of the clutch; and the first torque lead value is computedbased on the first pressure and a selected lead time and the secondtorque lead value is computed based on the second pressure and theselected lead time.

In another form, the present disclosure provides a method includingestimating a flow rate of a fluid in a clutch of a vehicle; estimating afirst pressure at a first location of the clutch based on the flow rate;computing a first torque lead value based on the first pressure, aselected lead time value, and a delay time value; computing a secondtorque lead value based on a second pressure, the selected lead timevalue, and the delay time value, the second pressure is estimated at asecond location of the clutch that is different than the first location;computing a third torque lead value by combining the first torque leadvalue and the second torque lead value; and applying torque from a motorof the vehicle based on the third torque lead value.

In variations of the method of the above paragraph, which can beimplemented individually or in any combination: the method furtherincludes computing the third torque lead value with a powertrain controlmodule coupled to the clutch and a combustion engine; the method furtherincludes providing the third torque lead value from the powertraincontrol module to a hybrid powertrain control module of the vehicle; themethod further includes controlling, with the hybrid powertrain controlmodule, the motor to provide the torque to the clutch based on the thirdtorque lead value; the flow rate of the fluid in the clutch of thevehicle is estimated by sensing a pressure of the fluid in a fluid lineof the clutch; and the first location is at a piston of the clutch andthe second location is at a valve of the clutch.

In another form, the present disclosure provides a method includingestimating a pressure at a piston of the clutch based on the flow rate;computing a first torque lead value based on the estimated pressure atthe piston, a selected lead time value, and a delay time value;computing a second torque lead value based on a pressure at a valve ofthe clutch, the selected lead time value, and the delay time value;computing a third torque lead value by combining the first torque leadvalue and the second torque lead value; and applying torque from a motorof the vehicle to an axle of the vehicle based on the third torque leadvalue, the axle of the vehicle is driven by the motor prior to computingthe third torque lead value.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

In order that the disclosure may be well understood, there will now bedescribed various forms thereof, given by way of example, referencebeing made to the accompanying drawings, in which:

FIG. 1 is a block diagram of a hybrid vehicle, according to someembodiments;

FIG. 2 is an illustration of a K0 clutch of a hybrid vehicle, accordingto some embodiments;

FIGS. 3A-3C are graphs of various torque signals associated with ahybrid vehicle, according to some embodiments;

FIG. 4 illustrates graphs of torque values associated with a transitionbetween operational modes of a hybrid vehicle, according to someembodiments; and

FIGS. 5-7 are flow diagrams of processes for operating a hybrid vehicle,according to some embodiments.

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various disclosedembodiments. However, one skilled in the relevant art will recognizethat embodiments may be practiced without one or more of these specificdetails, or with other methods, components, materials, etc. In otherinstances, well-known structures or methods associated with vehicleshave not been shown or described in detail to avoid unnecessarilyobscuring descriptions of the embodiments.

FIG. 1 is a block diagram of a hybrid vehicle 100, according to oneembodiment. The hybrid vehicle 100 includes an electric motor 102 and acombustion engine 104 coupled together by a K0 clutch 106. As will beset forth in more detail below, the hybrid vehicle 100 manages smoothtransitions between operational modes of the vehicle by using acombination of techniques to calculate a torque to be generated by themotor 102 during the transitions. The operational modes correspond towhether the motor 102, the combustion engine 104, or both the motor 102and the combustion engine 104 power the vehicle 100.

The vehicle 100 includes a drivetrain 111. The drivetrain includes atransmission 108 and an axle 110. The motor 102 is coupled to thetransmission 108. When the motor 102 powers the hybrid vehicle 100, themotor 102 applies torque to the axle 110 via the transmission 108. Thetransmission 108 and the axle 110 are part of the drivetrain of thehybrid vehicle 100. For simplicity in understanding principles of thepresent disclosure, the block diagram of FIG. 1 does not illustratevarious other components that are part of the drivetrain 111. Theseother components are well understood by those of skill in the art.

The K0 clutch 106 can be operated to couple or decouple the combustionengine 104 from the drivetrain 111. If the vehicle 100 transitions froman operational mode that solely uses the motor 102 to an operationalmode in which both the motor 102 and the combustion engine 104 powerdrivetrain 111, then the motor 102 will apply a torque to the K0 clutch106. The torque moves internal mechanical components of the K0 clutch106 to engage the combustion engine 104. The motor 102 also continues togenerate a torque to drive the drivetrain 111. During the transition,the motor 102 generates sufficient torque to both continue driving thedrivetrain 111 and to assist the K0 clutch 106 to engage the combustionengine 104.

If, during the transition, the motor 102 generates more torque that isneeded to both account for drag caused by the K0 clutch 106 and tomaintain the speed of the vehicle 100 by properly powering thedrivetrain 111, then the additional torque will be applied to thedrivetrain and may result in an unwanted acceleration of the vehicle100. If, during the transition, the motor 102 does not generate enoughtorque to both make up for the drag caused by the K0 clutch 106 and tomaintain the speed of the vehicle 100, then the torque supplied to thedrivetrain 111 may not be sufficient to maintain the speed of thevehicle 100. This may result in an unwanted deceleration of the vehicle100.

The vehicle 100 includes a hybrid powertrain control module (HPCM) 112.The HPCM 112 is coupled to the motor 102 and controls the operation ofthe motor 102. Among other functions, the HPCM 112 controls the amountof torque generated by the motor 102 and determines whether or not themotor 102 will assist the K0 clutch 106 to engage or disengage thecombustion engine 104.

The vehicle 100 includes a powertrain control module (PCM) 114. The PCM114 is coupled to the K0 clutch 106 and the combustion engine 104. ThePCM 114 receives sensor signals from the K0 clutch 106, as will bedescribed in more detail below. The PCM 114 controls the function of thecombustion engine 104. The PCM 114 is communicatively coupled to theHPCM of 112.

The HPCM 112 and the PCM 114 are electronic control modules of thevehicle 100. The HPCM 112 and the PCM 114 can each include one or morecomputer readable memories. The memories can store software instructionsfor the operation of the HPCM 112 and the PCM 114. The memories can alsostore data related to current and past values of sensor signals,commands received from other control modules or vehicle components,commands to be transmitted to other control modules or vehiclecomponents, and other types of data. The HPCM 112 and the PCM 114 caneach include one or more processors. The one or more processors canexecute software instructions stored in the one or more memories. Theone or more processors can generate commands to be applied to the motor102 and the combustion engine 104. The one or more processors cangenerate commands or signals to be transmitted to other control modulesof the vehicle 100. The HPCM 112 and the PCM 114 can be coupled viahardwired connections to each other and to the various components of thevehicle 100. The HPCM 112 and the PCM 114 can also be coupled viawireless connections to each other and to the various components of thevehicle 100.

In one embodiment, the PCM 114 estimates or calculates the additionaltorque that should be generated by the motor 102 during the transition.The additional torque will be applied to the K0 clutch 106 during thetransition to engage the combustion engine 104. The PCM 114 receivessensor signals from sensors associated with the K0 clutch 106 andgenerates the estimated torque that should be provided moment to momentby the motor 102 the K0 clutch 106. The PCM 114 provides the estimatedtorque values to the HPCM 112. The HPCM 112 then controls the motor 102to generate the estimated additional torque to engage the K0 clutch 106.

The amount of torque applied to the K0 clutch 106 during the transitionvaries throughout the transition. Furthermore, depending on the positionand type of sensors associated with the clutch 106, the sensor signalsmay provide current torque or pressure values that are different thanthe actual torque or pressure values at various components of the K0clutch 106. Additionally, there is lag or delay between torque beingrequested from the motor 102 to the K0 clutch 106 and the torqueappearing at components of the K0 clutch 106. Furthermore, there isfurther lag associated with torque signal transmission and sensor signaltransmission. All of these factors complicate the estimation of thetorque that should be applied by the motor 102 from moment to momentduring the transition.

In order to deal with these complications, the PCM 114 generates atorque lead value that accounts for signal lag, torque application lag,and imperfections in sensor signals due to sensor placement. The PCM 114generates the torque lead value based on two methods. The first methodgenerates a first torque lead value. The second method generates asecond torque lead value. The PCM 114 generates the torque lead value bycombining the first torque lead value and the second torque lead value.Respective weighting factors can be applied to the first and secondtorque lead values prior to combining them to generate the total torquelead value. Details related to the first and second methods forgenerating the first and second torque lead values are provided inrelation to FIG. 2 .

After the PCM 114 has generated the torque lead value, the PCM 114provides the torque lead value to the HPCM 112. The HPCM 112 then causesthe motor 102 to generate an additional amount of torque based on thetorque lead value and supplies the additional amount of torque to the K0clutch 106 during the transition. The torque lead value based on thefirst and second methods results in a smooth transition. In other words,the additional amount of torque generated by the motor 102 results inlittle or no acceleration or deceleration of the vehicle 100 during thetransition because the additional amount of torque is an accurateestimation of the amount of torque that should be generated by the motor102 from during the transition.

In one embodiment, the HPCM 112 generates the torque lead value bycombining first and second torque lead values. In this case, the PCM 114can apply sensor signals from sensors associated with the K0 clutch tothe HPCM 112. The HPCM 112 can then generate the torque lead value andcontrol the motor 102 in accordance with the torque lead value. Thesensors associated with the K0 clutch 106 may be directly coupled to theHPCM 112 in some embodiments. Various arrangements of control modulesand communication connections can be utilized without departing from thescope of the present disclosure.

FIG. 2 is a simplified illustration of a portion of the K0 clutch 106 ofFIG. 1 , according to one embodiment. The K0 clutch 106 includes a fluidline 118 and a valve 120. The K0 clutch 106 also includes a cylinder 122and a piston 124 positioned within the cylinder 122. A fluid 128 fillsthe fluid line 118.

The K0 clutch 106 couples the combustion engine 104 to the drivetrain111 by retracting the piston 124 within the cylinder 122 away from theend 123 of the cylinder 122. Movement of the piston 124 is accomplishedby forcing additional fluid 128 from the valve 120 into the fluid line118. In effect, pressure is applied from the valve 120 to force the flowof fluid 128 through the fluid line 118 into the cylinder 124. Thepressure pushes the piston 124 away from the end 123 of the cylinder122. As the piston 124 moves, the fluid 128 flows through the fluid line118 into the cylinder 124.

In the following description, references will be made to both pressureand torque associated with the K0 clutch 106. Pressure and torque arerelated to each other by a simple relationship:

P=k*T+C

where P is pressure, T is torque, C is a constant, and k is a conversionfactor. Accordingly, the torque lead value can be generated bygenerating a corresponding pressure lead value and then converting thepressure lead value to a torque lead value. Thus, generating the firstand second torque lead values can include first generating first andsecond pressure lead values and then converting the pressure lead valuesto the first and second torque lead values.

Movement of the piston 124 is based on the pressure at the head of thepiston 124. The pressure at the head of the piston 124 lags behind thepressure applied from the valve 120. The pressure at the valve 120 isapplied by a solenoid (not shown). This pressure can be referred to as acommand pressure.

The K0 clutch 106 includes a pressure sensor 126. The pressure sensor126 senses the fluid pressure within the fluid line 118 at a positionbetween the valve 120 and the cylinder 122. The pressure sensor 126generates sensor signals indicative of the fluid pressure. The sensorsignals are provided from the pressure sensor 126 to the PCM 114.Alternatively, the pressure sensor 126 can provide the pressure signalsto the HPCM 112.

The pressure at the head of the piston 124 is the factor that causes thepiston 124 to move, thereby causing the K0 clutch 106 to engage thecombustion engine 104. However, the pressure sensor 126 is not locatedat the head of the piston. The PCM 114 can estimate the pressure at thepiston 124 based on the flow rate Q of the fluid 128 within the fluidline 118. The flow rate Q can be calculated or estimated based on thefollowing formula:

Q=(1/Kvs)*(Pv−Ps)

where Kvs is a constant corresponding to a pressure resistance betweenthe valve 120 and the pressure sensor 126, Pv is the command pressure atthe valve 120, and Ps is the pressure at the pressure sensor 126. Thepressure Pp at the piston 124 can be estimated from the flow rate Qbased on the following relation:

Pp=Ps−Ksp*Q

where Ps is the pressure at the location of the pressure sensor, and Kspis a constant corresponding to a pressure resistance between thepressure sensor 126 and the piston 124. Plugging the formula for Q intothe equation above provides the following formula for the pistonpressure:

Pp=Ps−(Ksp/Kvs)*(Pv−Ps)

The first torque lead value TI1 can be calculated utilizing a firstmethod based on the estimated piston pressure Pp, which is in turn basedon the estimated flow rate Q. In particular, the first torque lead valueTI1 can be calculated by the following relationship:

TI1=Tp*(τc*s+1)/(τc−τl)*s+1)

where Tp is the torque at the piston 124, τc is a known time delaybetween the torque requested from request by the PCM 114 appearing at K0clutch 106, and τl is a selected lead time constant corresponding to thedelay of the motor 102 in generating torque commanded by the HPCM. II isless than TC. As described previously Tp can be estimated from Pp. Inone embodiment, TI1 can be generated by first generating a firstpressure signal by substituting Pp for Tp in the relationship above. TI1can then be generated by converting PI1 to TI1 based on the knownrelationship between pressure and torque described above. The meaning ofthe first torque lead value TI1 is described more fully in relation toFIG. 3A.

In an embodiment in which the first pressure lead value PI1 is generatedin place of or before generating a first torque lead value TI1, thefirst pressure lead value PI1 can be generated with the followingformula:

PI1=Pp*(τc*s+1)/(τc−τl)*s+1)

The PCM 114 generates a second torque lead value TI2 by a second method.The second method assumes that the K0 clutch response is a first-ordersystem based on the command pressure Pv at the valve 120, or thecorresponding command torque Tv at the valve 120. The second torquevalue is given by the following relationship:

TI2=Tv/((τc−τl)*s+1)

The meaning of the second torque lead value TI2 can be understood withrelationship to FIG. 3B. In an embodiment in which a second pressurelead value PI2 is generated in place of or before generating a secondtorque lead value TI2, the second pressure lead value PI2 can begenerated by the second method with the following formula:

PI2=Pv/(τc−τl)*s+1)

The total torque lead value TI is generated by combining the firsttorque lead value and the second torque and signal. As will beunderstood better with relation to FIGS. 3A-3C, the combination of thefirst and second torque lead values results in a total torque lead valueTI that accurately matches the actual torque that appears at the pistonhead, with a selected leadtime τl. In practice, the total torque leadvalue TI is generated by applying weighting values to the first andsecond torque lead values before combining the first and second torquelead values. The total torque lead value TI can be given by thefollowing relationship:

TI=w*TI2+(1−w)*TI1

where w is a weighting value between 0 and 1.

FIG. 3A is a graph illustrating various torque values versus time,according to one embodiment. With reference to FIGS. 1, 2, and 3A, thegraph of FIG. 3A illustrates a commanded torque, an actual torque, and afirst torque lead value TI1. The commanded torque is the desired torqueat K0 clutch 106 during a transition from a motor only mode of operationto a hybrid mode of operation that includes both the motor 102 and thecombustion engine 104. The actual torque is the value of the torque thatappears at K0 clutch 106 after the commanded pressure is applied to thevalve 120. The first torque lead value TI1 is a torque lead valuegenerated by the PCM 114 or the HPCM 112 using the first method asdescribed in relation to FIG. 2 .

As can be seen from FIG. 3A, when a torque is output by the K0 clutch106, there is a delay TC between the request of the torque by the PCM114 and the torque appearing at K0 clutch 106. In the example of FIG. 3Athe delay TC is about 100 ms, though other values of the delay arepossible based on the particular designs of the K0 clutch 106.Furthermore, the actual torque that appears at the piston 124 does notexactly mirror the command torque after the delay TC. The actual torquehas a peak that exceeds the peak of the command torque before settlingto the value of the command torque.

The first torque lead value TI1 is generated with the selected lead timeτl. The first torque lead value TI1 leads the actual torque by theselected lead time τl. The selected lead time τl is less than the delayTC. The selected lead time τl corresponds to the motor delay in torque.Accordingly, if the motor 102 is commanded a time τl before the actualtorque of the K0 clutch 106, then the torque delivered from the motorwill be aligned in time the actual K0 torque. In one example, theselected lead time τl is about 40 ms, though other values can beselected without departing from the scope of the present disclosure.

The first torque lead value TI1 has a peak that exceeds the peak of theactual torque. This is because the first method that generates the firsttorque lead value TI1 is an imperfect estimation of the actual torquewith the selected lead time τl. The selected lead time τl is a parameterthat can be selected/programmed by design engineers or that can beselected by the various control modules of the vehicle 100 based on thedelay of the motor 102 in producing torque.

FIG. 3B is a graph illustrating various torque values versus time,according to one embodiment. With reference to FIGS. 1, 2, and 3B, thegraph of FIG. 3B illustrates the command torque, the actual torque, anda second torque lead value TI2. The second torque lead value TI2 is atorque lead value generated by the PCM 114 or the HPCM 112 using thesecond method as described in relation to FIG. 2 .

The second torque lead value TI2 is generated with the selected leadtime τl. The second torque lead value TI2 leads the actual torque by theselected lead time τl. The second torque lead value TI2 has a peak thatis lower than the peak of the actual torque. This is because the secondmethod that generates the second torque lead value TI2 is an imperfectestimation of the actual torque with the selected lead time τl. Thus,from FIGS. 3A and 3B, we can see that the first torque lead value TI1overshoots the actual torque while the second torque lead value TI2undershoots the actual torque.

FIG. 3C is a graph illustrating various torque values versus time,according to one embodiment. With reference to FIGS. 1-3C, the graph ofFIG. 3C illustrates the command torque, the actual torque, the firsttorque lead value TI1, the second torque lead value TI2, and the totaltorque lead value TI correspond to a combination of the first and secondtorque lead values. As the first torque lead value TI1 overshoots theactual torque and the second torque lead value TI2 undershoots theactual torque, the combination of the first and second torque leadvalues results in a total torque lead value TI that more closely matchesthe actual torque, but with the selected lead time τl.

The vehicle 100 can utilize the torque lead value TI to control thetorque generated by the motor 102 during transitions between operationalmodes. The torque lead value can be utilized to generate, with the motor102, a torque that will result in a smooth transition betweenoperational modes of the vehicle 100. Less energy will be lost duringtransitions and safety will be improved.

As set forth previously, the first and second torque lead values may bemultiplied by respective weighting values. In one embodiment, theweighting values can be dynamically adjusted throughout the transition.In other words, the weighting values can be time-varying weightingvalues. In this case, the torque lead value TI can be represented by thefollowing formula:

TI=w(t)*TI2+(1−w(t))*TI1

where w(t) is a time varying weighting value.

The value of the time varying weighting factor w(t) can be generated orselected based on the state of the K0 clutch 106. For example, the timevarying weighting factor w(t) can vary based on the current stage of thetransition. Different weighting values can be used for the beginning ofthe transition, the middle of the transition, and the end of thetransition. The weighting value w(t) can have a first value while the K0clutch 106 is starting up, a second value while the combustion engine106 the starting up or beginning to generate torque, and a third valuewhile the clutch is locking. Various values for the weighting value w(t)can be utilized for various stages of the transition without departingfrom the scope of the present disclosure.

In one embodiment, the weighting factor w(t) can be dynamicallygenerated based on the magnitude of a normalized error. The error cancorrespond to the difference between a measured torque Tm and theexpected torque, Tinst, based on the torque lead signal TI. In oneexample, the normalized error err_(norm) can be calculated in thefollowing manner:

${err_{norm}} = {❘\frac{\left( {T_{m} - T_{inst}} \right)}{\left( {T_{cmd} - T_{inst}} \right)}❘}$

where Tcmd is a commanded torque. The weighting factor w(t) can vary asthe normalized error varies. Additionally, the weighting factor w(t) canhave a different upper limit based on the current stage of thetransition.

In one embodiment, the torque lead signal can be calculated in thefollowing manner:

T _(l) =T _(l1)+(1−w(t))·T _(cor)

where Tcor is a torque correction value. The torque correction value canbe calculated in the following manner:

Tcor=Tm−Tinst

where Tinst is the expected torque based on the most recent previousvalue of the torque lead signal TI. In this example, the torque leadsignal is based on the first torque lead signal TI1, the time varyingweighting value w(t), and the torque correction value Tcor.

FIG. 4 illustrates graphs 400 and 402 indicating torques associated withtransitions between a motor only operational mode and a combination ofmotor and combustion engine operational mode, according to oneembodiment. FIG. 4 will be described with reference to FIG. 1-3C. Thegraph 400 indicates the torque output by the motor during thetransition. The transition begins at time T0 and ends at time T3. As canbe seen from the graph 400, the torque provided by the motor 102increases beginning at time TO in order to compensate for dragintroduced to the drivetrain while the K0 clutch 106 engages thecombustion engine 104.

The graph 402 includes the torque lead signal 406. The torque leadsignal 406 is calculated in accordance with the combination of methodsdescribed previously in relation to FIGS. 1-3C. As can be seen from thegraph 402, the torque lead signal 406 leads the actual torque outputfrom the motor 102 as shown in the graph 400. For example, the torquelead signal 406 begins to increase before the time TO. In particular,the torque lead signal 406 leads the actual torque by the selected leadtime τl.

The graph 402 also illustrates the K0 clutch capacity 408. The K0 clutchcapacity 408 aligns with the timing of the torque output by the motor102 during the transition as indicated in the graph 400. The K0 clutchcapacity 408 can affect the performance of the vehicle 100 during thetransition. In particular, after the combustion engine 104 starts up,the combustion engine 104 outputs a torque. If the torque output by thecombustion engine during the transition exceeds the capacity of the K0clutch 106, then there may be slippage in the K0 clutch 106.

To avoid slippage in the K0 clutch 106, the vehicle 100 estimates thecapacity of the K0 clutch throughout the transition. The vehicle 100limits the torque output from the combustion engine 104 to a value lessthan the current capacity of the K0 clutch 106. This helps prevent anyslippage in the K0 clutch 106 during the transition.

In one embodiment, the vehicle 100 estimates the capacity of the K0clutch 106 based on the piston pressure of the K0 clutch 106. Inparticular, the capacity of the K0 clutch is estimated by estimating thepiston pressure based on the pressure sensed by the pressure sensor 126,as described above, but without the selected lead time. The estimatedpiston pressure is then converted to an estimated piston torque, asdescribed above. The estimated piston torque is continuously updatedthroughout the transition. The estimated piston torque corresponds tothe estimated capacity 408 of the K0 clutch. During the transition, thevehicle 100 limits the torque output by the combustion engine 104 to avalue less the estimated capacity 408 of the K0 clutch.

The PCM 114 can generate the estimated the estimated K0 clutch capacity408 based on the pressure sensor 126. The PCM supplies a torque commandsignal to the combustion engine 104. The combustion engine 104 outputs atorque in accordance with the torque command signal. The PCM 114 limitsthe torque command signal provided to the combustion engine 104 to avalue less than the estimated K0 clutch capacity 408.

FIG. 5 is a process 500 for operating a vehicle during the transitionbetween operational states of the vehicle, according to one embodiment.The process 500 can utilize components, systems, and processes describedin relation to FIGS. 1-3C. At 502, the process 500 begins. Thedescription of FIG. 5 will be made with reference to FIGS. 1, 2, and 3A.At 504, the process 500 determines whether the pressure at the pressuresensor is higher than a threshold pressure. In one example, the PCM 114or the HPCM 112 receives sensor signals from the pressure sensor 126 anddetermines whether the pressure at the pressure sensor 126 is higherthan a threshold pressure. If the pressure at the pressure sensor ishigher than the threshold pressure, the process 500 proceeds to 506.

At 506, the process 500 estimates the output pressure at the valve ofthe K0 clutch. At 506 the process 500 determines the pressure differencebetween the valve and the pressure sensor. In one example, the PCM 114or the HPCM 112 estimates the valve pressure based on the torquesupplied by the motor 102. The PCM 114 or the HPCM 112 then determinesthe pressure difference between the valve 120 and the pressure sensor126. From 506, the process 500 proceeds to 508.

At 508, the process 500 estimates the fluid flow through the fluid line118 of the K0 clutch 106. As described previously in relation to FIG. 2, the flow rate Q of fluid within the fluid line 118 of the K0 clutch106 can be estimated based on the pressure difference between the valve120 and the pressure sensor 126 and the pressure resistance value Kvsrepresenting the pressure resistance between the valve 120 and thesensor 126. The PCM 114 or the HPCM 112 can make the estimation of theflow rate Q.

Returning to 504, if the pressure at the pressure sensor is lower thanthe threshold, the process 500 proceeds to 510. At 510, the process 500sets the flow rate within the piston 124 of the K0 clutch 106 to 0. Inone example, the PCM 114 or the HPCM 112 sets the value of the flow rateto 0. From 510 or 508, the process 500 proceeds to 512.

At 512, the process 500 estimates the pressure difference between thepressure sensor 126 and the piston 124. In one example, the PCM 114 orthe HPCM 112 can estimate the pressure difference between the pressuresensor 126 and the piston 124. The pressure difference between thepressure sensor 126 and the piston 124 can be generated based on theflow rate Q and the pressure resistance value Ksp corresponding to thepressure resistance between the pressure sensor 126 and the piston 124.From 512, the process proceeds to 514.

At 514, the process 500 determines the pressure at the piston 124. Asdescribed previously in relation to FIG. 2 , the pressure at the pistoncan be determined based on the pressure at the pressure sensor 126, thepressure output at the valve 120, and the pressure resistance constantsKsp and Kvs. In one example, the PCM 114 or the HPCM 112 can determinethe pressure at the piston 124. From 514, the process proceeds to 516.

At 516, the process 500 generates the first pressure lead value usingthe first method. The description of FIG. 2 detailed determining a firsttorque lead value TI1 using the first method. However, as previouslynoted, a simple conversion enables torque to be calculated from pressureor pressure to be calculated from torque. Accordingly, in oneembodiment, a first pressure lead value PI1 is generated using the firstmethod. The first method generates the pressure lead value based on thepressure at the piston 124, the delay time TC, and the selected leadtime τl. In one example, the PCM 114 or the HPCM 112 can generate thefirst pressure lead value.

At 518, the process 500 generates the second pressure lead value PI2utilizing the second method. As described previously, the second methodgenerates the second pressure lead value PI2 based on the commandpressure at the valve 120, the delay time TC, and the selected lead timeτl. The description of FIG. 2 detailed determining a second torque leadvalue TI2 using a second method. However, as noted above, a secondpressure lead value can be generated using the first method butsubstituting pressure values for torque values. In one example, the PCM114 or the HPCM 112 can generate the second pressure lead value. Afterthe first and second pressure lead values are generated at 516 and 518,the process 500 proceeds to 520.

At 520, the process 500 generates a total pressure lead value PI bycombining the first pressure lead value PI1 and the second pressure leadvalue PI2. The combination can include multiplying the first and secondpressure lead values PI1 and PI2 by respected weighting factors, asdescribed previously in relation to FIG. 2 . The PCM 114 or the HPCM 112can generate the total pressure lead value PI. from 520, the processproceeds to 522.

At 522, the process 500 determines the total torque lead value TI byapplying a pressure-to-torque transfer function. In one example, the PCM114 or the HPCM 112 can generate the total torque link signal TI. At524, the process 500 ends.

FIG. 5 provides an example in which the torque lead value TI isgenerated by first generating first and second pressure lead values byrespective first and second methods. This may be convenient because thepressure sensor 126 provide pressure signals that can be readily use ingenerating the first pressure lead value. However, as has been describedpreviously, the torque lead value TI can be generated by directlygenerating first and second torque lead values TI1 and TI2 rather thanby first generating first and second pressure lead values PI1 and PI2.

Examples have been given in which the PCM 114 or the HPCM 112 performvarious estimations and calculations. However, depending on theconfiguration of the vehicle 100, other control modules can be utilizedto perform the calculations and estimations utilized in generating thetorque lead value TI.

FIG. 6 is a flow diagram of a method 600 for operating a hybrid vehicle,according to one embodiment. The method 600 can utilize components,systems, and processes described in relation to FIGS. 1, 2, 3A, 3B, 3C 4and 5. At 602, the method 600 includes estimating a flow rate of a fluidin a K0 clutch of a vehicle by sensing a pressure of the fluid in afluid line of the K0 clutch. At 604, the method 600 includes estimatinga pressure at a piston of the K0 clutch based on the flow rate. At 606,the method 600 includes computing a first torque value based on thepressure at the piston and the selected lead time. At 608, the method600 includes computing a second torque lead value based on a pressure ata valve of the K0 clutch and a selected lead time. At 610, the method600 includes computing a third torque lead value by combining the firsttorque lead value and the second lead torque value. At 612, the method600 includes applying torque from a motor of a vehicle based on thethird torque value.

FIG. 7 is a flow diagram of a method 700 for operating a hybrid vehicle,according to one embodiment. The method 700 can utilize components,systems, and processes described in relation to FIGS. 1, 2, 3A, 3B, 3C,and 4-6 . At 702, the method 700 includes driving an axle of a vehiclewith a motor. At 704, the method 700 includes computing a first torquelead value with a control module of the vehicle based on a first torquegeneration formula. At 706, the method 700 includes computing a secondtorque lead value with the control module of the vehicle based on asecond torque generation formula. At 708, the method 700 includescomputing a third torque lead value by combining the first torque leadvalue and the second torque lead value. At 710, the method 700 includesenabling, with a K0 clutch, a combustion engine to assist in driving theaxle. At 712, the method 700 includes applying a torque with the motorbased on the third torque lead value while enabling the combustionengine with the K0 clutch and limiting the torque of the combustionengine to the K0 clutch torque.

In one embodiment, a method includes estimating a flow rate of a fluidin a K0 clutch of a vehicle by sensing a pressure of the fluid in afluid line of the K0 clutch, estimating a pressure at a piston of the K0clutch based on the flow rate, and computing a first torque value basedon the pressure at the piston and the selected lead time. The methodincludes computing a second torque lead value based on a pressure at avalve of the K0 clutch and a selected lead time, computing a thirdtorque lead value by combining the first torque lead value and thesecond lead torque value, and applying torque from a motor based on thethird torque value.

In one embodiment, a vehicle includes an axle, a motor configured todrive the axle, and a combustion engine. The vehicle includes a K0clutch coupled between the motor and the combustion engine andconfigured to selectively enable the combustion engine to drive theaxle. The vehicle includes a first control module coupled to the K0clutch and con d to generate a first lead torque value, a second torquelead value, and a third torque lead value based on the first and secondtorque lead values.

In one embodiment, a method includes driving an axle of a vehicle with amotor, computing a first torque lead value with a control module of thevehicle based on a first torque generation formula, and computing asecond torque lead value with the control module of the vehicle based ona second torque generation formula. The method includes computing athird torque lead value by combining the first torque lead value and thesecond torque lead value, enabling, with a K0 clutch, a combustionengine to assist in driving the axle, and applying a torque with themotor based on the third torque lead value while enabling the combustionengine with the K0 clutch.

The various embodiments described above can be combined to providefurther embodiments. Aspects of the embodiments can be modified, ifnecessary, to employ concepts of the various patents, applications andpublications to provide yet further embodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

Unless otherwise expressly indicated herein, all numerical valuesindicating mechanical/thermal properties, compositional percentages,dimensions and/or tolerances, or other characteristics are to beunderstood as modified by the word “about” or “approximately” indescribing the scope of the present disclosure. This modification isdesired for various reasons including industrial practice, material,manufacturing, and assembly tolerances, and testing capability.

As used herein, the phrase at least one of A, B, and C should beconstrued to mean a logical (A OR B OR C), using a non-exclusive logicalOR, and should not be construed to mean “at least one of A, at least oneof B, and at least one of C.”

In this application, the term “controller” and/or “module” may refer to,be part of, or include: an Application Specific Integrated Circuit(ASIC); a digital, analog, or mixed analog/digital discrete circuit; adigital, analog, or mixed analog/digital integrated circuit; acombinational logic circuit; a field programmable gate array (FPGA); aprocessor circuit (shared, dedicated, or group) that executes code; amemory circuit (shared, dedicated, or group) that stores code executedby the processor circuit; other suitable hardware components (e.g., opamp circuit integrator as part of the heat flux data module) thatprovide the described functionality; or a combination of some or all ofthe above, such as in a system-on-chip.

The term memory is a subset of the term computer-readable medium. Theterm computer-readable medium, as used herein, does not encompasstransitory electrical or electromagnetic signals propagating through amedium (such as on a carrier wave); the term computer-readable mediummay therefore be considered tangible and non-transitory. Non-limitingexamples of a non-transitory, tangible computer-readable medium arenonvolatile memory circuits (such as a flash memory circuit, an erasableprogrammable read-only memory circuit, or a mask read-only circuit),volatile memory circuits (such as a static random access memory circuitor a dynamic random access memory circuit), magnetic storage media (suchas an analog or digital magnetic tape or a hard disk drive), and opticalstorage media (such as a CD, a DVD, or a Blu-ray Disc).

The apparatuses and methods described in this application may bepartially or fully implemented by a special purpose computer created byconfiguring a general-purpose computer to execute one or more particularfunctions embodied in computer programs. The functional blocks,flowchart components, and other elements described above serve assoftware specifications, which can be translated into the computerprograms by the routine work of a skilled technician or programmer.

The description of the disclosure is merely exemplary in nature and,thus, variations that do not depart from the substance of the disclosureare intended to be within the scope of the disclosure. Such variationsare not to be regarded as a departure from the spirit and scope of thedisclosure.

What is claimed is:
 1. A method comprising: estimating a first pressureat a first location of a clutch based on a flow rate of a fluid in theclutch; computing a first torque lead value based on the first pressure;computing a second torque lead value based on a second pressure;computing a third torque lead value by combining the first torque leadvalue and the second torque lead value; and applying torque from a motorof the vehicle based on the third torque lead value.
 2. The method ofclaim 1, further comprising computing the third torque lead value with apowertrain control module coupled to the clutch and a combustion engine.3. The method of claim 2, further comprising providing the third torquelead value from the powertrain control module to a hybrid powertraincontrol module of the vehicle.
 4. The method of claim 3, furthercomprising controlling, with the hybrid powertrain control module, themotor to provide the torque to the clutch based on the third torque leadvalue.
 5. The method of claim 1, further comprising: driving an axle ofthe vehicle with the motor prior to computing the third torque leadvalue; and enabling a combustion engine of the vehicle to drive the axleby coupling the combustion engine with a drivetrain of the vehicle withthe clutch, wherein the third torque lead value compensates for theclutch coupling the combustion engine to the drivetrain.
 6. The methodof claim 1, further comprising driving an axle with both a combustionengine and the motor after enabling the combustion engine to drive theaxle.
 7. The method of claim 1, further comprising generating the firstand second torque lead values based, in part, on a time delay valuecorresponding to a delay in providing torque from the motor.
 8. Themethod of claim 7, further comprising generating the first and secondtorque lead values based, in part, on the time delay value and aselected lead time value less than the time delay value.
 9. The methodof claim 1 further comprising: generating the first torque lead valueby: generating a first pressure lead value based on a piston pressureand a selected lead time; and applying a transfer function to the firstpressure lead value; and generating the second torque lead value by:generating a second pressure lead value based on a pressure at a valveand the selected lead time; and applying a transfer function to thesecond pressure lead value.
 10. The method of claim 1, wherein the flowrate of the fluid in the clutch of the vehicle is estimated by sensing apressure of the fluid in a fluid line of the clutch.
 11. The method ofclaim 1, wherein the second pressure is estimated at a second locationof the clutch, the second location being different than the firstlocation.
 12. The method of claim 11, wherein the first location is at apiston of the clutch and the second location is at a valve of theclutch.
 13. The method of claim 1, wherein the first torque lead valueis computed based on the first pressure and a selected lead time and thesecond torque lead value is computed based on the second pressure andthe selected lead time.
 14. A method comprising: estimating a flow rateof a fluid in a clutch of a vehicle; estimating a first pressure at afirst location of the clutch based on the flow rate; computing a firsttorque lead value based on the first pressure, a selected lead timevalue, and a delay time value; computing a second torque lead valuebased on a second pressure, the selected lead time value, and the delaytime value, the second pressure is estimated at a second location of theclutch that is different than the first location; computing a thirdtorque lead value by combining the first torque lead value and thesecond torque lead value; and applying torque from a motor of thevehicle based on the third torque lead value.
 15. The method of claim14, further comprising computing the third torque lead value with apowertrain control module coupled to the clutch and a combustion engine.16. The method of claim 15, further comprising providing the thirdtorque lead value from the powertrain control module to a hybridpowertrain control module of the vehicle.
 17. The method of claim 16,further comprising controlling, with the hybrid powertrain controlmodule, the motor to provide the torque to the clutch based on the thirdtorque lead value.
 18. The method of claim 14, wherein the flow rate ofthe fluid in the clutch of the vehicle is estimated by sensing apressure of the fluid in a fluid line of the clutch.
 19. The method ofclaim 14, wherein the first location is at a piston of the clutch andthe second location is at a valve of the clutch.
 20. A method,comprising: estimating a flow rate of a fluid in a clutch of a vehicleby sensing a pressure of the fluid in a fluid line of the clutch;estimating a pressure at a piston of the clutch based on the flow rate;computing a first torque lead value based on the estimated pressure atthe piston, a selected lead time value, and a delay time value;computing a second torque lead value based on a pressure at a valve ofthe clutch, the selected lead time value, and the delay time value;computing a third torque lead value by combining the first torque leadvalue and the second torque lead value; and applying torque from a motorof the vehicle to an axle of the vehicle based on the third torque leadvalue, wherein the axle of the vehicle is driven by the motor prior tocomputing the third torque lead value.